1. Field of the Invention
The present invention relates to a hollow golf club head made from metal, and particularly relates to a golf club head having a wood type shape or another shape close to the wood type shape.
2. Description of the Related Art
Hollow golf club heads made from metal are used broadly as wood type golf club heads such as drivers or fairway woods. Generally, as shown in FIG. 4, a wood type hollow golf club head 1 includes a face portion 2 for hitting a ball therewith, a crown portion 3 forming the top portion of the golf club head, a sole portion 4 forming the bottom portion of the golf club head, a side portion 5 forming the side portion on the toe side, back side and heel side of the golf club head, and a hosel portion 6. A shaft 7 is inserted into the hosel portion 6 of the golf club head 1, and fixed thereto by an adhesive agent or the like. Incidentally, recently, many golf club heads called utility golf club heads have appeared on the market. As one kind of utility golf club head, various golf club heads similar to the wood type golf club head (that is, including a face portion, a sole portion, a side portion and a crown portion) are available on the market.
Aluminum alloys, stainless steel or titanium alloys are available as metal for forming such hollow golf club heads. Of them, titanium alloys have been used broadly in recent years.
JP-A-2002-119625 discloses a golf club head in which a face portion is made thicker than a crown portion, the crown portion is curved upward, and the face portion and the crown portion are molded integrally by press working.
In order to increase the carry of a shot with a metal hollow golf club head, development has been made and aimed at increasing the repulsion of a ball by use of bending of the face surface, to thereby hit the ball farther. However, when a golfer having a low head speed uses such a golf club head, the deformation of the face surface is so small that the effect of increasing the initial velocity of a ball is insufficient. In addition, a low trajectory of the ball may hinder increase of the carry.
According to the golf club head disclosed in JP-A-2002-119625, the crown portion is bent upward at the time when a ball is hit, so that the repulsion of the ball is enhanced. However, the face portion and the crown portion different in thickness are pressed integrally in the golf club head disclosed in JP-A-2002-119625. Such press working on members different in thickness requires a high degree of difficulty in working in view of working technology. Thus, the efficiency in manufacturing the golf club head is lowered.